Lecture 6: Interfaces

Interfaces: what services and access are provided?
The interface is in effect a contract between the supplier and the customer. The desire is to provide services that are uniform and convenient, with enough functionality to be easy to use but not so much as to become unwieldy.
Information Hiding: What information is visible and what is private?
An interface must provide straightfoward access to the components while hiding the details of the implementation so they can be changed without affecting users.
Resource Management: who is responsible for managing memory and other resources?
Here, the main problems are allocating and freeing storage, and managing shared copies of information.
Error handling: who detects errors, who reports them, and how? When an error is detected, what recovery is attempted?

CSV - Comma separated values
CSV - Prototype library
CSV - A library for others
CSV - A C++ implementation
Interface Principles
1. Hide implementation details
2. Choose a small orthogonal set of primitives
3. Don't reach behind the user's back
4. Do the same thing the same way everywhere
Resource Management
1. Free a resource in the same layer that allocated it
Abort, Retry, Fail?
1. Detect errors at a low level, handle them at a high level
2. Use exceptions only for exceptional situations

Created: Jan. 27, 2005 () by jjohnson@cs.drexel.edu